/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.catalina.tribes.tipis;

import org.apache.catalina.tribes.Channel;
import org.apache.catalina.tribes.ChannelException;
import org.apache.catalina.tribes.Member;
import org.apache.catalina.tribes.UniqueId;
import org.apache.catalina.tribes.util.Arrays;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;

import java.io.Serializable;

/**
 * A smart implementation of a stateful replicated map. uses primary/secondary backup strategy.
 * One node is always the primary and one node is always the backup.
 * This map is synchronized across a cluster, and only has one backup member.<br/>
 * A perfect usage for this map would be a session map for a session manager in a clustered environment.<br/>
 * The only way to modify this list is to use the <code>put, putAll, remove</code> methods.
 * entrySet, entrySetFull, keySet, keySetFull, returns all non modifiable sets.<br><br>
 * If objects (values) in the map change without invoking <code>put()</code> or <code>remove()</code>
 * the data can be distributed using two different methods:<br>
 * <code>replicate(boolean)</code> and <code>replicate(Object, boolean)</code><br>
 * These two methods are very important two understand. The map can work with two set of value objects:<br>
 * 1. Serializable - the entire object gets serialized each time it is replicated<br>
 * 2. ReplicatedMapEntry - this interface allows for a isDirty() flag and to replicate diffs if desired.<br>
 * Implementing the <code>ReplicatedMapEntry</code> interface allows you to decide what objects
 * get replicated and how much data gets replicated each time.<br>
 * If you implement a smart AOP mechanism to detect changes in underlying objects, you can replicate
 * only those changes by implementing the ReplicatedMapEntry interface, and return true when isDiffable()
 * is invoked.<br><br>
 * <p>
 * This map implementation doesn't have a background thread running to replicate changes.
 * If you do have changes without invoking put/remove then you need to invoke one of the following methods:
 * <ul>
 * <li><code>replicate(Object,boolean)</code> - replicates only the object that belongs to the key</li>
 * <li><code>replicate(boolean)</code> - Scans the entire map for changes and replicates data</li>
 * </ul>
 * the <code>boolean</code> value in the <code>replicate</code> method used to decide
 * whether to only replicate objects that implement the <code>ReplicatedMapEntry</code> interface
 * or to replicate all objects. If an object doesn't implement the <code>ReplicatedMapEntry</code> interface
 * each time the object gets replicated the entire object gets serialized, hence a call to <code>replicate(true)</code>
 * will replicate all objects in this map that are using this node as primary.
 * <p>
 * <br><br><b>REMEMBER TO CALL <code>breakdown()</code> or <code>finalize()</code> when you are done with the map to
 * avoid memory leaks.<br><br>
 * TODO implement periodic sync/transfer thread
 *
 * @author Filip Hanik
 * @version 1.0
 */
public class LazyReplicatedMap<K, V> extends AbstractReplicatedMap<K, V> {
	private static final long serialVersionUID = 1L;
	private final Log log = LogFactory.getLog(LazyReplicatedMap.class);


//------------------------------------------------------------------------------    
//              CONSTRUCTORS / DESTRUCTORS
//------------------------------------------------------------------------------   

	/**
	 * Creates a new map
	 *
	 * @param channel         The channel to use for communication
	 * @param timeout         long - timeout for RPC messages
	 * @param mapContextName  String - unique name for this map, to allow multiple maps per channel
	 * @param initialCapacity int - the size of this map, see HashMap
	 * @param loadFactor      float - load factor, see HashMap
	 */
	public LazyReplicatedMap(MapOwner owner, Channel channel, long timeout, String mapContextName, int initialCapacity, float loadFactor, ClassLoader[] cls) {
		super(owner, channel, timeout, mapContextName, initialCapacity, loadFactor, Channel.SEND_OPTIONS_DEFAULT, cls, true);
	}

	/**
	 * Creates a new map
	 *
	 * @param channel         The channel to use for communication
	 * @param timeout         long - timeout for RPC messages
	 * @param mapContextName  String - unique name for this map, to allow multiple maps per channel
	 * @param initialCapacity int - the size of this map, see HashMap
	 */
	public LazyReplicatedMap(MapOwner owner, Channel channel, long timeout, String mapContextName, int initialCapacity, ClassLoader[] cls) {
		super(owner, channel, timeout, mapContextName, initialCapacity, AbstractReplicatedMap.DEFAULT_LOAD_FACTOR, Channel.SEND_OPTIONS_DEFAULT, cls, true);
	}

	/**
	 * Creates a new map
	 *
	 * @param channel        The channel to use for communication
	 * @param timeout        long - timeout for RPC messages
	 * @param mapContextName String - unique name for this map, to allow multiple maps per channel
	 */
	public LazyReplicatedMap(MapOwner owner, Channel channel, long timeout, String mapContextName, ClassLoader[] cls) {
		super(owner, channel, timeout, mapContextName, AbstractReplicatedMap.DEFAULT_INITIAL_CAPACITY, AbstractReplicatedMap.DEFAULT_LOAD_FACTOR, Channel.SEND_OPTIONS_DEFAULT, cls, true);
	}

	/**
	 * Creates a new map
	 *
	 * @param channel        The channel to use for communication
	 * @param timeout        long - timeout for RPC messages
	 * @param mapContextName String - unique name for this map, to allow multiple maps per channel
	 * @param terminate      boolean - Flag for whether to terminate this map that failed to start.
	 */
	public LazyReplicatedMap(MapOwner owner, Channel channel, long timeout, String mapContextName, ClassLoader[] cls, boolean terminate) {
		super(owner, channel, timeout, mapContextName, AbstractReplicatedMap.DEFAULT_INITIAL_CAPACITY,
				AbstractReplicatedMap.DEFAULT_LOAD_FACTOR, Channel.SEND_OPTIONS_DEFAULT, cls, terminate);
	}

	//------------------------------------------------------------------------------
//              METHODS TO OVERRIDE    
//------------------------------------------------------------------------------
	@Override
	protected int getStateMessageType() {
		return AbstractReplicatedMap.MapMessage.MSG_STATE;
	}

	@Override
	protected int getReplicateMessageType() {
		return AbstractReplicatedMap.MapMessage.MSG_BACKUP;
	}

	/**
	 * publish info about a map pair (key/value) to other nodes in the cluster
	 *
	 * @param key   Object
	 * @param value Object
	 * @return Member - the backup node
	 * @throws ChannelException
	 */
	@Override
	protected Member[] publishEntryInfo(Object key, Object value) throws ChannelException {
		if (!(key instanceof Serializable && value instanceof Serializable)) return new Member[0];
		Member[] members = getMapMembers();
		int firstIdx = getNextBackupIndex();
		int nextIdx = firstIdx;
		Member[] backup = new Member[0];

		//there are no backups
		if (members.length == 0 || firstIdx == -1) return backup;

		boolean success = false;
		do {
			//select a backup node
			Member next = members[nextIdx];

			//increment for the next round of back up selection
			nextIdx = nextIdx + 1;
			if (nextIdx >= members.length) nextIdx = 0;

			if (next == null) {
				continue;
			}
			MapMessage msg = null;
			try {
				Member[] tmpBackup = wrap(next);
				//publish the backup data to one node
				msg = new MapMessage(getMapContextName(), MapMessage.MSG_BACKUP, false,
						(Serializable) key, (Serializable) value, null, channel.getLocalMember(false), tmpBackup);
				if (log.isTraceEnabled())
					log.trace("Publishing backup data:" + msg + " to: " + next.getName());
				UniqueId id = getChannel().send(tmpBackup, msg, getChannelSendOptions());
				if (log.isTraceEnabled())
					log.trace("Data published:" + msg + " msg Id:" + id);
				//we published out to a backup, mark the test success
				success = true;
				backup = tmpBackup;
			} catch (ChannelException x) {
				log.error("Unable to replicate backup key:" + key + " to backup:" + next + ". Reason:" + x.getMessage(), x);
				continue;
			}
			try {
				//publish the data out to all nodes
				Member[] proxies = excludeFromSet(backup, getMapMembers());
				if (success && proxies.length > 0) {
					msg = new MapMessage(getMapContextName(), MapMessage.MSG_PROXY, false,
							(Serializable) key, null, null, channel.getLocalMember(false), backup);
					if (log.isTraceEnabled())
						log.trace("Publishing proxy data:" + msg + " to: " + Arrays.toNameString(proxies));
					getChannel().send(proxies, msg, getChannelSendOptions());
				}
			} catch (ChannelException x) {
				//log the error, but proceed, this should only happen if a node went down,
				//and if the node went down, then it can't receive the message, the others
				//should still get it.
				log.error("Unable to replicate proxy key:" + key + " to backup:" + next + ". Reason:" + x.getMessage(), x);
			}
		} while (!success && (firstIdx != nextIdx));
		return backup;
	}


}